I am only going to start with spraying about 3-4 lawns per year for broadleaf control. I cant afford a $2000+ spray rig and cant justify it. I already have in my posession a length of hose (200ft), a tank (75-100 gal, Im not exactly sure yet but I will find out) and a Briggs & Stratton 5.5HP Horizontal shaft motor mounted on a half sheet of plywood. This is connected to some kind of pump by a pulley and belt system and I know for a fact the pump is junk and does not work. Now for the questions: 1) How many gpm do I need coming out of the pump feeding my hose and handgun? (this question will tell me what kind of pump to get). I do not want too much pressure and start blowing hoses, and I dont want too little pressure. I can do the math to figure out the RPM's and pulley ratios for this system. 2) What about agitation? Do I need to be agitating while I am spraying? I was just planning on running a hose from the tank, to the pump, then a valve that sent the mix either to the handgun hose or directly back into the top of the tank. I need a filter in there somewhere too I believe... 3) Do I need any kind of pressure regulators? Keep in mind that I want to do this as cheap as possible. I would go buy a pre-made rig if i was going to go into business doing this but I just want to spray 3-4 yards a year. Any advice would be appreciated, and any details on anything I forgot would also be great.